From the mid-1940's, it was known that metal alkoxide could be hydrolyzed and condensed to form glasses. Subsequently, from about the mid-1970's, it was known that silica could be produced in situ as a chemical product of compounds such as tetraethoxysilane (TEOS).
It was previously known from U.S. Pat. No. 3,811,918 to partially acid hydrolyze silicon alkoxide and add metal oxide to prepare a glass precursor which could be fired to a glass composition at a temperature above 1000.degree. C. Further U.S. Pat. No. 4,346,131 describes the preparation of a clear alcohol solution of acid hydrolyzed metal alkoxide which can be coated on a substrate and dried to produce an optical coating.
Silane coupling agents, including TEOS, as disclosed in U.S. Pat. No. 4,480,072, provided a useful means to crosslink hydroxylated polymers.
An article on SOL-GEL DERIVED DIP COATINGS by Helmut Dislich of Schutt Glaswerke, Hattenbergstr. 10, 6600 Mainz, Federal Republic of Germany, discloses how mixtures of metal alkoxides may be used to condense mixed metals on a glass surface such as silicon-titanium, aluminum-magnesium, cadmium-tin and indium-tin. An article on ORGANICALLY MODIFIED SILICATES AS INORGANIC-ORGANlC POLYMERS by H. K. Schmidt of Fraunhofer-Institut fur Silicatforschung, Wurzburg, Federal Republic of Germany, describes combinations of linear organic polymer networks with three dimensional tetrahedron silicon structures using the sol-gel process, e.g. where combined polymerization of methacrylate and condensation of Ti(OR).sub.4 /Si(OR).sub.4 /epoxy-Si(OR).sub.3 produce a reinforced system with increased tensile strength and scratch resistance.
Japanese Application 86/25,739 discloses antifogging tile coatings where silica is bonded to polyvinyl alcohol using hydrolyzed [3-(glycidyloxy)propyl]trimethoxysilane.
Lin et al, U.S. Pat. No. 4,731,264, discloses an organoalkoxysilane/alumina coating composition which is applied to a plastic transparency. The coating composition is the reaction product of an alumina sol prepared by mixing aluminum isopropoxide and glacial acetic acid, methyl triethoxysilane and gamma glycidoxypropyl trimethoxysilane.